Floating covering for liquid storage tank

Abstract

A floating covering on the liquid content of a storage tank. The circumferential edge of the covering has an elastic annular body provided with a gas-tight annular chamber and an annular body of foam material. Pressure control means communicates with the chamber for selectively pressurizing and releasing pressure from the chamber.

I claim: 
     
       1. In a storage tank having a cylindrical side wall with an open top and having an inner surface enclosing a space in which liquid is to be stored, disk-like cover means for floating on the liquid, the cover means having a nominal diameter smaller than the nominal diameter of the inner surface of the side wall to define a circumferential margin providing an annular gap between such circumferential margin and the inner surface of the side wall, annular closing body means joined to the cover means for bridging said gap and effecting a circumferential seal against said inner wall, said annular closing body means comprising an elastic annular body portion defining a gas-tight annular chamber having a nominal diameter greater than that of said circumferential margin but smaller than that of the inner surface and presenting an annular hollow space and an annular body portion of foam material interposed between said annular hollow space and the circumferential margin of the cover means, and pressure control means communicating with said hollow space for selectively pressurizing and releasing pressure from said hollow space. 
     
     
       2. In a storage tank as defined in claim 1 including a layer or body of material having a low coefficient of friction on the surface of the annular closing body means which faces said inner wall. 
     
     
       3. In a storage tank as defined in claim 1 wherein said cover means is in the form of a sheet of flexible material and including zipper means joining said sheet of flexible material to the annular closing body means. 
     
     
       4. In a storage tank as defined in claim 3 wherein said annular closing body means comprises an annulus of foamed material having a hollow interior, said annular elastic body portion being in the form of an endless elastic hose received in said hollow interior. 
     
     
       5. In a storage tank as defined in claim 4 wherein said annulus of foamed material comprises a number of segments threaded onto said hose. 
     
     
       6. In a storage tank as defined in claim 6 wherein said annular closing body means comprises an elastic body defining said chamber presenting said annular hollow space and a second chamber disposed radially inwardly of said hollow space, said second chamber being filled with said foam material. 
     
     
       7. In a storage tank as defined in claim 6 wherein said annular closing body means presents a concave outer margin and including a lens shaped body of material of low coefficient of friction filling such concave outer margin. 
     
     
       8. In a storage tank as defined in claim 1 wherein said annular closing body means comprises an annulus of foamed material having a hollow interior, said annular elastic body portion being in the form of an endless elastic hose received in said hollow interior. 
     
     
       9. In a storage tank as defined in claim 8 wherein said annulus of foamed material comprises a number of segments threaded onto said hose. 
     
     
       10. A floating cover assembly for the liquid content of a storage tank which comprises the combination of a disk-shaped cover having a peripheral edge of lesser diameter than the storage tank so as to present a gap between the cover and the storage tank, an annular closing body bridging the gap, said annular closing body comprising a radially and circumferentially expandable and contractible annulus of composite form, one part of said composite form being an annular part of foamed material bounding the peripheral edge of the cover and a second part of said composite form being an endless annular elastic gas-tight member bounding said annular part of foamed material which bounds the peripheral edge of the cover and defining a pressure chamber, and pressure control means communicating with said pressure chamber for selectively pressurizing and releasing pressure from said pressure chamber to radially and circumferentially expand and contract said annular closing body. 
     
     
       11. A floating cover assembly as defined in claim 10 including a layer or body of material having a low coefficient of friction on the outer surface of the annular closing body which faces said storage tank.